Making the default playlist timespan configurable.
Merge branch 'timespanconfig' of github.com:rmca/grafana into rmca-timespanconfig
Added config setting for default playlist timespan
fixed issue with influxdb datasource introduced in recent filterSrv refactoring
Add an influxdb setting 'avoid_empty_data' (false by default). Useful
when you have a list of influxDB urls (load-balancing style) and you
want grafana to hit each one of them until it finds data.

Very handy if you *partition* your data in multiple influxdb hosts (or
datacenters) and want to show the data of them in the same graph.